Romania Enters the War

Romania declared war on Austria-Hungary, lured by Allied promises of Transylvania, Bukovina, and Banat. Romanian forces invaded Transylvania with 370,000 men, achieving initial successes. However, a counteroffensive by Falkenhayn from the north and Mackensen from the south overran most of Romania within four months. Bucharest fell on December 6, 1916. Romania's oil fields became vital to Germany's war effort.